import java.util.Scanner;

public class demo01 {
//数的计算
    public static int count=0;
    public static void main(String[] args) {
        Scanner sc=new Scanner(System.in);
        int n=sc.nextInt();
        fib(n);
        System.out.println(count);
    }
    public static void fib(int n){
        count++;
        for (int i = 1; i <= n/2; i++) {
            fib(i);
        }
    }
}
